In recent years, in order to reduce greenhouse effect gases such as carbon dioxide regarded as a cause of the global warming, further energy saving has been required in a facility such as a building and a factory. Following this, introduction of renewable energy generated from photovoltaic power generation and wind power generation, from which the greenhouse effect gases are not emitted at the time of power generation, has been being accelerated.
The renewable energy utilizes natural energy such as sunlight and wind power, which is taken out phenomena that repeatedly occur in the natural environment, and accordingly, has a disadvantage that there occur fluctuations such that an amount of power generation is reduced owing to a weather situation.
At present, a fluctuation amount of the power generation is absorbed by being compensated by outputs from thermal power generation and the like. However, it is apprehended that the fluctuation amount of the power generation may come not to be fully absorbed as an introduction ratio of the renewable energy is being enhanced.
As another means for absorbing the fluctuation amount of the power generation, it is conceived to utilize a storage battery and a standby generator. However, the storage battery has a problem that cost per unit power storage amount is high. Moreover, the standby generator has a problem that it costs to own assets, and that the standby generator concerned is inefficient since the standby generator consumes energy at the time of being on standby in an activated state.